As long as livestock farming has existed, it has always been necessary to herd animals, protecting them against predators and accidents, and keeping them together for making the loss of animals as low as possible.
Even today, traditional herding, which has been used for thousands of years where one or more persons always follow the flock as long as they are on free pasture, is the most common.
Naturally, this old fashioned herding is very expensive as it continuously occupies human recourses in a very ineffective way. This is the reason why many farmers have decided to skip herding, but, as a consequence, by the end of the season the loss of animals has been considerable. However, there is an increasing demand in the public opinion for high food quality, but also for a good treatment of the animals in their lifetime.
One way of remotely tracking animals is to place a VHF radio transmitter on the individual animals of interest and determining their approximate positions based upon the signal strength of the radio signals from the transmitter at a receiver. This solution has traditionally been used for scientific purposes on wild individual animals. It is not designed for collecting data other than for an approximate position, and each monitored individual animal must be provided with a long distance transmitter, which will be relatively expensive for a whole flock. Besides, a transmitter also transmitting additional condition data, e.g., body temperature and humidity, would be rather heavy.
From U.S. Pat. Nos. 5,868,100 and 5,791,294, U.S. patent application 2002/0021219 and European patent application EP 945060 there are known a number of more or less similar systems for tracking and monitoring animals. Each monitored animal is wearing an electronic device comprising communication and positioning equipment. The positioning equipment is a GPS unit. Such devices tend to become heavy and are therefore not suited for young animals. In addition, the devices are costly. Thus, such systems are less applicable for tracking and monitoring flocks of livestock; they are used nearly exclusively for monitoring single individual animals for scientific purposes.
Consequently, there is a need for a system remotely tracking animals in a flock with a minimum of heavy equipment and with the possibility of monitoring the condition and health of the animals.